Substituted unsaturated aldehydes



United States Pattitit This invention relates to new alpha, alpha-dialkyl substituted unsaturated aldehydes having the structural formula 'll Ra-C-CHO in which R; and R are saturated allcyl groups or together form a saturated alicyclic ring and R is an allyl group or an alkyl-substituted allyl group. These alpha, alpha-dialkyl substituted unsaturated aldehydes can be hydrogenated to the corresponding alpha,-alpha-di-alkyl substituted saturated alcohols, the carboxylic acid esters of which are useful as oxidation-resistant plasticizers. They can also be oxidized to the corresponding alpha, alpha-dialkyl substituted alkenoic acids, the esters of which are useful monomers for the preparation of resinous polymers.

I have found that these novel alpha,alpha-d ialkyl substituted unsaturated aldehydes can be prepared by distilling, from a catalytic amount of an acidic catalyst, an acetal of an alpha,alpha-dialkyl substituted saturated aldehyde having the structural formula R1 1 cncno in which R; and R have the same significance as 'aboye, with an unsaturated aliphaticalcoholR OH;.in'1-which R is the same'as R above except that the position of the double bond may be diiferent; The acetal has the structural formula The alkenyl group derived from the unsaturated alcohol becomes attached to the alpha carbon atom of theraldehyde not through the carbon which had been attached to the oxygen, but through the carbon at the other end of the chain, with a shift in the position of the double bond. Virtually any type of acidic catalyst is satisfactory for the reaction. Mineral acids such as phosphoric acid, sulfuric acid, p-toluenesulfom'c acid; boron trifluoride, calcium chloride, ammonium chloride; acidic ion exchange resins, acid clays; and strong organic acids such as formic, oxalic, trichloroacetic, and trifluoroacetic are satisfactory.

Example 1.--Isobutyraldehyde diallyl acetal (389.5 g.) to which 0.2 g. of "85 phosphoric acid had been added was distilled through a one-foot'Vigreux column at a rate such as to maintain the still-pot temperature at 130-140 Y5 C. Over a 2 /2 hour period, 370 g. of distillate wascollected at a head temperature of 95-117 C. The distillate was washed threetimes with 500-1111. portions of water to remove the allyl alcohol, which is water soluble.

The remaining organiclayer was distilled through an I .Pa tented Aug. 2,1960

on, Ocmcmcn.

CH.CH' C O.G'H,.CH:OH|

lsobutyraldehyde diallylacetal 'CHI 0H,:(uremia.cnoq-oflnoncmon H: V 2,2-dlmethyl-4pentenal allyl alcohol Example 2.-2-Methylbutyraldehyde' diallyl acetal (251 g.) to which 0.1 g. of phosphoric acid had been added was distilled as in Example 1, with a pot temperature of -160 C., to give 242.5 g. of distillate at 96-15 1 C. After removal of allyl alcohol by washing with water, distillation gave 119g. of 2-ethyl-2- methyl-4-pente nal at C., n 1.43 13. Further distillation of the residue gave an additional 33 g. of the starting 2-methy1butyraldehyde diallyl acetal, B.P. 134- 143 C. at 150 mm. pressure. Based on the acetal consumed, the yield of 2-ethyl-2-methyl-4-pentenal was 82%; The 2,4-dinitrophenylhydrazone of the 2-ethyl-2- methyl-'4-pentenal melted at 113-114" C. and contained 54.95% carbon and 5.83% hydrogen; theoretical for C H Q,N; is 54.8% carbon 5.88% hydrogen.

7 ocmcmom I? omomonc V H| OCH1.CH:CH z-methylbutyraldehyde diallylacetal orn 0H,:OILOHsiL HO+CH=zQROHlOH I 2-ethyl-2-methyl-4-pentenal allyl alcohol Example 3.-I-sobutyraldehyde dimethallyl acetal (411.5 g. to which 0.2 ml. of 85% phosphoric acid had been added was distilled through a 1-foot Vigreuxv column. Over a 2 /2 hour period, 397.5 g. of distillate was collected at 113-14l C. while the pot temperature was 149-158 C. Fractional distillation gave 146' g. of methallyl alcohol, B.P. l.12-114 C., and 190.6 g; (a 73% yield) of 2,2,4-trimethyl-4-pentenal, B.P. l47.5-148 C., n 1.4321; Analysis of the aldehyde showed 76.16% carbon and 11.30% hydrogen, as compared with calculated values of 76.2% carbon and'1.1.l8% hydrogen.

.The 2,4-dinitrophenylhydrazone melted at lid-[132 'C.

7 When-theunsaturated alcoholris allyl alcohol' or a 1- substituted and/or 3-substituteda1lyl alcohol, the alpha,

3 alpha-dialkyl substituted unsaturated aldehyde may be prepared directly from the -alpl1a,alpha-dialkyl substituted saturated aldehyde and the unsaturated aliphatic alcohol, by heating one mole of the alcohol with at least one mole of the saturated aldehyde in the presence of an acidic catalyst and a high-boilinginertsolvent,- undr conditions such that Water is removed azeotropically. This process has the advantage of not requiring recovery of the unsaturated alcohol. This one-step reaction is notapplicable to 2 su-bstituted allyl alcohols, or toi 1,1- or 3,3-disubstituted allyl alcohols. 2-suhstitutd allyl alcohols are too readily isomerized by acidic catalysts to aldehydes or ketones, and 1,1- or 3,3-disubstituted allyl alcohols undergo loss 911 water to give dienes with great ease. V

Example 4.--A mixture of 108 g. (1.5 moles) of isobutyraldehyde, 58 g. (1 mole) of allyl alcohol, 200 g. of

Example 7.--A mixture of 159 g. (2.21 moles) of isobutyraldehyde, 147 g. (1.71 moles) of 1-penten-3-ol, 0.3 g. of p-toluenesulfonic acid, and 313 g. of diphenyl ether was refluxed under a 2-ft. packed column topped by a Dean-Stark trap for 20 hours. During this time the pot temperature rose from 96 to 164 C., and 32.5 ml. of water layer wascollected (theoretical 30.8 ml.). Distillation at atmospheric pressure gave 35.5 g. of recovered isobutyraldehyde (theoretical 36 g.), a 10 g. intermediate cut, and 213 g. (an 89% yield) of trans- 2,2dimethyl4-hepteual, B.P. l67168 C., n 1.4 320. Hydrogenation of the latter compound over Raney nickel give, in 93%. yield, 2,2-dimethylheptano1, B.P. 191-192 p-cymene, and 0.25 g. of p-toluenesulfonic acid was refluxed under a distillation column topped by a water separator for 32 hours. During'this time the pot temperature rose slowly from 83 C. to 140 C., and 20.5 ml. of water layer (probably containing a little allyl alcohol) was separated. Fractional distillation of the reaction mixture gave 22.1 g. of isobutyraldehyde at 62-65 C., a 1.9 g. intermediate cut, and 101.1 g. (an 89% yield) of 2.2- dimethyl-4-pentenal at 124-126 C., n 1.4200. The residue weighed 210 g. and may have contained a small amount of the diallyllacetal of 2,2-dimethy14-pentenal.

Example 5 Four hundred forty-eight grams (4 moles) of cyclohexanecarboxaldehyde, 242 g. (4.17 moles) of allyl alcohol, 60 ml. of benzene and 0.5 g. of p-toluenesulfonic acid were mixed and heated under a packed column topped by a Dean-Stark water separator for 22 hrs. During this time the pot temperature rose from 114 to 158 C. and 82 m1. of water layer (containing some dissolved allyl alcohol) was separated. Distillation of the reaction mixture gave, after removal of benzene and a small forerun, 512 g. (an 84% yield) of 1-allylcyclohexanecarboxaldehyde, B.P. 105-107 C.

at 32 mm., 12 1.4701, and 56 g. of residue.

CH2 HzC CELCHO l +2CHa2CH.CH2OH- H1O on, 7

cyclohexane allyl alcohol carboxaldehyde /CE2 /CH2.CHICH2 mo 3-ono HzC 7 CH2 CH2 lallyl-cyclohexanecarboxaldehyde Example 6.-In like manner a mixture of 248 g. (2 moles) of norcamphane-Z-carboxaldehyde, 121 g. (2.08 moles) of allyl alcohol, 50 ml. of benzene, and 0.2 g. of p-toluene sulfom'c-acid was refluxed for hours, during which time 43 ml. of water layer was separated. Distillation of the reaction product gave 295 g. (a 91% yield) of 2-allyl-norc'amphane-2-carboxaldehyde, B.P. 120 C.

at 26 mm., 11 1.4894.

OH.CHO+CHs.CH .CH.CH:CH-+-- CH3 H isobutyrmama-3:01 aldehyde 1 CH3.CH3.CH CH: 7

CH.CH2.(|3.CHO

trans-2,2-dimethyl-4-heptenal Example 8.--1-Allyl-cyclopentanecarboxaldehyde, B.P. 137-140 C. at 200 mm., n 1.4622, was obtained in 72% yield from allyl alcohol and cyclopentanecarboxaldehyde using the one-step process described in Examples 3-6.

H2O ORCHO +2CHzZCH.CHzOH- H2 0 C H:

cyclopentaneallyl alcohol oarboxaldehyde I a 7 CH (3112.011: CH2 H2? ?-0 H O nzc-'-cnr l-allyl-cyelopentane oarboxaldehyde R5 R, Rs;OH:( .CHg.( J.CHO

from an acetal of a saturated aldehyde having the for- ,mula

\zacno R. with an unsaturated a ienate alcohol having "the" forlafl: 7 s.

l g R B, eerie-(Bade ,1:

R and R being saturated hydrocarbon groups which together comprise from 2 to 6 carbon atoms and which may, together with the carbon atom to which they are attached, constitute an alicyclic ring, and R and R being each selected from the group consisting of hydro gen, methyl and ethyl, which process comprises heating the acetal in the presence of an acidic catalyst and distilling the product aldehyde from the reaction mixture.

8. A process of preparing an aldehyde having the formula directly iirom an unsaturated aliphatic alcohol having the formula 0 CHzzOIELCHOH and a saturated aldehyde having the formula CELOHO R and R being saturated hydrocarbon groups which together comprise item 2 to 6 carbon atoms and which may, together with the carbon atom to which they are attached, constitute an alicyclic ring, and R being selected from the group consisting of hydrogen, methyl and ethyl, which comprises heating one mole of the al cohol with at least one mole of the saturated fldehyde in the presence of an acidic catalyst and a high-boiling inert solvent, While removing water azeotropically from the react-ion mixture.

References Cited in the file of this patent UNITED STATES PATENTS Saunders Mar. 21, 1950 

1. A SUBSTITUATED UNSATURATED ALDEHYDE SELECTED FROM THE GROUP CONSISTING OF 2,2-DIMETHYL-4-PENTENAL, 2-ETHYL2-METHYL-4-PENTENAL, 2,2,4-TRIMETHYL-4-PENTENAL, 2,2-DIMETHYL-4-HEPTENAL, 1-ALLYL-CYCLOHEXANE, CARBOXALDEHYDE, 1-ALLYL-CYCLOPENTANECARBOXALDEHYDE,AND 2-ALLYL-NORCAMPHANE-2-CARBOXALDEHYDE. 